(1) Field of the Invention
The present invention relates to a method for driving a gas-discharge display panel comprising a matrix of picture elements consisting of pairs of display discharge cells and auxiliary discharge cells provided individually with three electrode, one of which is common to both cells, a pulse train having predetermined intervals and pulse widths being continuously applied between electrodes of the display discharge cells, so as to sustain a once started sequence of pulse discharge until a discharge climinating pulse is applied thereto.
(2) Description of the Prior Art
A typical method for driving a gas-discharge display panel of the above kind, in each picture element of which a display anode, a holed cathode and an auxiliary anode are stacked in order, has been disclosed by the present applicant. According to this driving method, driving pulses having such waveforms as shown in FIG. 1 are applied to those electrodes respectively. That is, the display anode A is continuously applied with a discharge sustaining pulse train having a pulse width .tau., a pulse height V.sub.AS and an interval T, and, when a picture information is to be displayed by starting a gas-discharge in the display discharge cell, the cathode K and the auxiliary anode A' are simultaneously applied with a negative pulse having a pulse height V.sub.KF and a positive pulse having a pulse height V.sub.A'F respectively at an interval T-.tau. which does not contain the discharge sustaining pulse, so as to prevent the generation of erroneous discharges caused by the overlap of those pulses. In the display discharge cell, after the gas-discharge is continued by the discharge sustaining pulse during the duration .tau., this pulse gas-discharge is ordinarily stopped during the above interval T-.tau.. However, charged particles generated by the pulse gas-discharge are not extinguished simultaneously with the stopping of the gas-discharge and hence are reserved in a certain time duration, so as to lower a re-ignition voltage of the discharge cell. Accordingly, another pulse gas-discharge is easily generated again by the succeeding discharge sustaining pulse under the appropriate selection of the length of the interval T, and, as a result, those pulse gas-discharges are repeated successively by each pulse of the discharge sustaining pulse train. The pulse height V.sub.AS and the pulse width .tau. of the discharge sustaining pulse are selected in such a manner that, when any preceding gas-discharge has not been caused in the display discharge cell, no pulse gas-discharge is generated, whilst, once any gas-discharge is generated, the aforesaid re-ignition phenomenon is caused, and further that, when the gas discharge is generated in the auxiliary discharge cell, a new gas-discharge can be started and sustained. Consequently, when the gas-discharge is generated in the auxiliary discharge cell by the pulses applied simultaneously to the cathode K and the auxiliary anode A', the sequence of the pulse discharges is started in the display discharge cell immediately after the auxiliary discharge is generated. That is, the entry of the picture information to be displayed, which is effected by the starting of the pulse discharge in the display discharge cell, is controlled by the starting of the gas-discharge in the auxiliary discharge cell.
On the other hand, when it is required to stop the sequence of pulse discharges continued by the discharge sustaining pulse train in the display discharge cell, the display anode A and the cathode K are simultaneously applied with a pair of discharge eliminating pulses having the pulse heights V.sub.AE and V.sub.KE respectively as shown in FIG. 1, so as to lower the effective voltage of the discharge sustaining pulse applied to the display discharge cell and hence to prevent the continuation of the aforesaid sequence of pulse discharges. Once the sequence of pulse discharges is discontinued as mentioned above, the pulse discharge cannot be regenerated by applying the discharge sustaining pulse having the pulse height V.sub.AS thereafter.
Regarding the above mentioned conventional method for driving the gas-discharge display panel, the elimination of gas-discharge does not cause any difficulty, whilst the entry of picture information and the sustenance of gas-discharge cause the following difficulties.
Regarding the waveforms of the driving pulses of various kinds as shown in FIG. 1, the possible range of the pulse height V.sub.AS of the discharge sustaining pulse should be set up as follows. EQU V.sub.fmin &gt;V.sub.AS &gt;V.sub.fpmax ( 1) EQU V.sub.AS &gt;V.sub.zmax ( 2)
where V.sub.fmin is the lowest among all of the gas-discharge cells of the discharge starting pulse voltages applied to the display discharge cells with the pulse width .tau., V.sub.fpmax is the highest among all of the gas-discharge cells of the discharge starting pulse voltages applied to the display discharge cells under the existence of the auxiliary discharge, and V.sub.zmax is the highest among all of the gas-discharge cells of the lowest pulse voltages V.sub.z required individually for sustaining the pulse discharges in the display discharge cells.
On the other hand, the pulse discharge of the aforesaid kind can be stably sustained without any current limiting resistor by reducing the pulse width .tau. as narrow as possible. However, when the pulse width .tau. is narrowed excessively such as a few micro seconds, the above voltage V.sub.fpmax cannot help being raised, even if under the existence of the auxiliary discharge, because a hole provided through the cathode for ionized coupling between cells is formed as small as possible for reducing the background brightness caused by the auxiliary discharge to the utmost. Particularly, when it is required to shorten the time taken for the entry of picture information such as in the display of television, the time taken for the auxiliary discharge is required to be shortened also, so that an insufficient amount of ionized particles generated by the auxiliary discharge can be diffused into the display discharge cell and hence the above voltage V.sub.fpmax is further raised. Consequently, it is necessary to determine the range of the above voltage V.sub.fpmax by the equation (1) alone, although it can be expected to be determined by both of those equations (1) and (2) as mentioned above. Moreover, it means to narrow the possible range of the voltage V.sub.AS that the amount of the term V.sub.fpmax is increased in the equation (1), and, as a result, it causes another difficulty such as the margin of the pulse height of the discharge sustaining pulse is reduced. In addition, the increase of the voltage V.sub.AS of the discharge sustaining pulse causes also the increase of the current of the pulse discharge, the loads impressed on the electrodes and the driving circuit thereof, as well as the excessive power consumption accompanied by the above may damage the display panel. Furthermore, in the gas-discharge display panel which employs the fluorescent material radiated by the excitation of the gas-discharge, the above increase of the discharge current causes still another difficulty such as the efficiency of the radiation thereof is lowered.
As described above in detail, the conventional method for driving the gas-discharge display panel has various defects such as the voltage range of the discharge sustaining pulse train is narrowed, as well as the pulse height thereof cannot help being raised and hence the increase of the discharge current accompanied thereby causes various kinds of injurious effects.